In trauma, the brain is violently shaken, which can cause multiple small shear type injuries across many areas of the brain, as the brain is very delicate and collides with the rough interior of the skull.

Then the bodies response to the initial injury sets in train a number of secondary causes

Initial injuries can lead to swelling which causes secondary damage, as the brain encased within the skull has no room to allow for this expansion.

Swelling can cut off the supply of oxygen to neurons (brain cells), which can then die in a matter of minutes.

Damage to the blood vessels in the brain lining from initial trauma can also cause neuron death due to lack of oxygen.

Blood vessels also serve as a radiator to cool the brain, overheating can cause neuron death.

Lack of blood and oxygen trigger a chemical reaction called ischemic cascade, which is responsible for most neuron death.

Damaged and dead neurons can release the neurotransmitters stored within their vesicles, which can over stimulate other neurons leading to further damage.

This damage to the brain, both in terms of neuron death and the severing of connections between neurons is the physiological cause of the mental impairments observed in brain injured people.

Medical advancements in preventing secondary injuries such as anoxia and ischemic cascade have lead to people surviving brain injury far more frequently than was the case in the past. This increase in frequency of survival is the reason why services such as Headway are in increasing demand. Immediate post trauma care may have become very effective in helping brain injured people to survive, but it is then necessary for the family, carers and the survivors themselves to adapt to living with the injury and attempting to recover as best as is possible – a process that will take many years or possibly the rest of their lives.